1. Field of the Invention
The present invention relates to an image forming apparatus (e.g., a laser printer), and to a developer cartridge to be removably mounted in the image forming apparatus.
2. Description of the Related Art
Conventionally, a developer cartridge which contains a toner is removably mounted in a laser printer. Such a laser printer includes new cartridge detection unit which judges whether or not the mounted developer cartridge is new and determines the service life of the new developer cartridge.
New cartridge detection unit proposed, for example, in Japanese Unexamined Patent Publication No. 2000-221781 includes a sector gear provided in a developer cartridge and having a projection and a recess. When the developer cartridge is newly mounted in an image forming apparatus body, the projection of the sector gear enters a new cartridge detection sensor to turn on the new cartridge detection sensor. When driving of an idler gear is started after the mounting of the developer cartridge, the sector gear is rotated to move the projection from the new cartridge detection sensor to a used cartridge detection sensor, whereby the projection enters the used cartridge detection sensor to turn on the used cartridge detection sensor. At the same time, the idler gear reaches the recess of the sector gear to stop the rotation of the sector gear.
Further, new cartridge detection unit proposed, for example, in Japanese Unexamined Patent Publication No. 2005-55544 and US Unexamined Patent Publication No. 2005031359 includes a third intermediate gear and a detection gear provided in a developer cartridge removably mounted in a laser printer, and an actuator provided in a main body frame of the laser printer. Power is inputted to the third intermediate gear. The detection gear has an abutment member, and is irreversibly moved from a new cartridge position at which the detection gear is not meshed with the third intermediate gear to a used cartridge position at which the detection gear is not meshed with the third intermediate gear through a power transmission position at which the detection gear is meshed with the third intermediate gear. The actuator is brought into abutment against the abutment member of the detection gear to move the detection gear from the new cartridge position to the power transmission position when the developer cartridge is mounted.